This invention relates to a pointing device and more particularly to a sensitive and short height pointing device that is still able to generate sufficient strain.
Index input devices are widely used in various types of input devices such as control panels, keyboards, remote control devices and other electronic devices. The index input device may be in the form of a mouse, a joy stick, a touch pad, a track ball, a pointing stick and the like. The basic principle of the index input device is to generate analog signals based on strain resulting from force applied on the index device in a selected direction. The analog signal output is then used by a computer for performing a required function. In the market, the pointing bar can be found in some notebook computers. It is generally located between keys in the keyboard. Through the strain incurred, the respective user""s application direction and the strength may be thus realized by the computer to further determine the moving direction and distance of the cursor.
In the development of pointing bar means, how to increase force sensitivity to thus reduce the required force for generating signals is a highly focused subject. Eudo et al disclose in U.S. Pat. No. 5,640,178 a pointing bar means generally shown in FIG. 7. As shown, the pointing bar means has a resilient bracket 1 mounted on a base 6 above a recess 6A by means of a plurality of fasteners 7. Above the bracket 1, a bar 2 is provided. Below the bottom surface of the bracket 1, a plurality of strain gauges 3 are provided. When the bar 2 receives an external force, the bracket 1 above the recess 6A is deformed, and the strain gauges 3 sense the strain resulting from the deformation to produce analog signals.
Since the bar 2 has to receive the external force and the bracket 1 has to be screwed to the base 6 by the fasteners 7, the whole structure of the pointing bar means becomes complicated and has an excessive height. Furthermore, the strain being produced is small due to the fasteners 7 tight fastening of the bracket 1; i.e., the strain gauge 3 cannot produce sufficient strain. Therefore, overall sensitivity of the pointing bar means is thus very low.
In view of aforesaid disadvantages, it is an object of this invention to provide a sensitive and short height pointing device that has a simple structure with cantilever arms for generating sufficient strain to enhance operation sensitivity.
The pointing device according to this invention includes a substrate, a sensing member and a rubber member for shrouding the sensing member over the substrate. The sensing member has at least one protrusive cantilever arm upon which a strain signal generator can be located. When the rubber member subjects to an external force, the rubber member is then squeezed and deformed, and consequently induces respective strain in the cantilever arm. The strain signal generator then senses the strain and produces signal output.
In one aspect of this invention, the strain signal generator is preferably located adjacent to one end of the cantilever arm, either at an upper surface or a lower surface of the arm for producing analog signals resulting from the strain in the arm. The strain signal generator may be a strain gauge, a piezoelectric member and the like.
In one embodiment of this invention, a separator may be sandwiched between the sensing member and the substrate for the cantilever arm to have a larger deforming space thereunder. The separator may be a circuit board, a simple partition and the like which has a desired thickness. The separator has a smaller surface dimension than the sensing member for the cantilever arm to maintain suspending condition relative to the substrate. The substrate may have an opening under the cantilever arm so that the rubber member may be deformed easier while subjected to an external force.
In another embodiment of this invention, the sensing member and the substrate may be integrally formed together by pressing operation or by adhering the sensing member to the substrate. The cantilever arm may be made by pressing or formed an angle against the substrate surface. The substrate may also have an opening formed below the cantilever arm to enable the rubber member be squeezed and deformed easily.
The rubber member is elastic and can be deformed to a substantial extend under external force. It may be made of rubber, rubber sheet and the like.